Rotary abrasive tool

ABSTRACT

A plurality of pre-assembled abrasive units are removably mounted on the periphery of a cylindrical but, and each includes a pad of multiple abrasive-coated plies fastened together at their inner ends by an anchor clip formed for retention in slots in the hub. Each overlying ply is of successively shorter length, and the plies form at their outer ends multiple stepped abrading surfaces which define a self-dressing finishing surface for rotation against the work surface. The plies are bowed into an arcuate shape and a predetermined flexibility to maximize the exposed finishing surface and soften it for improved abrading and service life characteristics.

I United States Patent [15] 3,653,856 Field 5] Apr. 4, 1972 [541 ROTARY ABRASIVE TOOL 2,597,421 5/1952 White .51/334 Inventor: Albert Field Clo Field Abrasive Manf. 3,512,311 5/1970 Block ..51/334 Co lnc., 1303 Stanley Avenue, Dayton, Primary Examiner Donald 6 Kelly Ohio 45404 AttorneyMarechal, Biebel, French & Bugg {22] Filed: Mar. 20, 1970 [57] ABSTRACT [21] App]. No.: 21,386 I A plurality of pre-assembled abrasive units are removably I mounted on the periphery of a cylindrical but, and each in [52] US. Cl ..51/334, 51/407 cludes a pad of multiple abrasive-coated plies fastened [51] ..B24d 13/04 together at their inner ends by an anchor clip formed for re- [58] Field of Search ..51/334, 336, 337, 401, 405, tention in slots in the hub. Each overlying ply is of successively 51/407 406 shorter length, and the plies form at their outer ends multiple stepped abrading surfaces which define a self-dressing finish- 56] References Cited ing surface for rotation against the work surface. The plies are bowed into an arcuate shape and a predetermined flexibility to UNlTED STATES PATENTS maximize the exposed finishing surface and soften it for improved abrading and service life characteristics. 2,423,992 7/1947 Nordgren ..5l/334 2,826,776 3/1958 Peterson ..51/336 X 4 Claims, 4 Drawing Figures April 4 1972 Patten lA/l/E/VTUI? ALBERT FIELD ATTOIZVEYS ROTARY ABRASIVE TOOL BACKGROUND OF THE. INVENTION In rotary abrasive devices of the type used for internal finishing of tubular bores an the like, usually one or more superposed abrasive plies are secured in retaining slots spaced longitudinally on the periphery of a central hub. Commonly, the plies are of equal length and are permanently anchored in the longitudinal slots, such as by adhesives as disclosed in U.S. Pat. No. 2,871,632, and extend radially outwardly in a substantially straight line. These rotary abrasive devices are generally used for deburring, finishing or polishing the internal surfaces of cylinders and the like.

The substantially straight plies are relatively rigid, but they usually have sufficient flexibility to bend rearwardly and adjust themselves to the internal diameter of the cylinder as they rotatably engage the work surface. When initially bent rearwardly in this manner, the leading ply of the pack is the only abrading surface contacting the work surface. Thereafter an adjusting process occurs, and the leading ply and successive plies are gradually worn down to the point that most of the plies will contact the surface and perform the abrading function.

As the plies are gradually worn down during the adjusting process they form multiple self-dressing surfaces, but each such surface has a relatively small exposed area. The wiping effect of the plies is accordingly diminished because only the outer edges of the successive plies wipe the work surface. In addition, after the relatively rigid plies are bent rearwardly, they are inherently biased and press against the work surface. These plies therefore tend to scratch the surface because they do not satisfactorily flex with burrs or imperfections protruding from the work surface, and consequently do not produce the finest abrading function.

The abrasive particles on the surface of the relatively rigid and straight standing plies also tend to engage the work surface obliquely, rather than tangentially. These abrasive particles accordingly tend to be sheared off at the outer edges of the plies, rather than worn down smoothly, and the service life of the abrasive tool is substantially reduced.

The deficiencies of present abrasive devices have been described above, and the ideal rotary abrasive tool is one which will not only minimize these deficiencies but also will satisfactorily perform the different abrading operations under the diverse conditions encountered in the art. In addition, for convenience, the ideal abrasive too] should have abrasive plies which are removably mounted on the hub so they can be readily replaced when they are worn down.

SUMMARY OF THE INVENTION The present invention is directed to an improved rotary abrasive tool and to a pre-assembled abrasive unit for use therewith. In general, the invention provides an abrasive tool with a plurality of pre-assembled and removably mounted abrasive units defining a substantially circumferential abrasive surface which contacts the work surface tangentially, and has an increased surface area and a longer service life.

The abrasive units are mounted on the hub by endwise insertion into longitudinal slots formed in the peripheral surface of a rotatable hub, and the slots are formed for retaining the units against movement in the radial direction. A pair of side disks or plates are secured to the sides of the hub and retain the abrasive units against axial movement during rotation of the tool against a work surface.

In accordance with a preferred embodiment of the invention, each abrasive unit includes a pad of overlying abrasive sheets which are fastened at their inner ends in an anchor clip formed for removable insertion with a corresponding slot in the central hub. Each overlying ply is of successively shorter length, and the plies form at their outer ends multiple stepped abrading surfaces which combine to define a peripheral selfdressing abrading surface.

The plies are bowed into an arcuate shape and a predetermined flexibility by breaking them over a roller or rollers at various angles with respect to their longitudinal axis. The arcuate shape enlarges the exposed abrasive area of the stepped abrading surfaces and permanently sets the plies for tangential engagement with the work surface. In addition, the enlarged exposed area gives the self-dressing abrading surface an expanded service life capability.

The flexibility obtained by breaking the plies over rollers effectively eliminates rigidity from the individual plies and softens them so that they are less likely to scratch the work surface. This increased flexibility, coupled with the increased exposed abrading area, also serves to wipe the work surface more effectively and to produce a high quality abrading finishes.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation, partly in section, showing the preferred form of the abrading tool of the present invention disposed within a cylinder;

FIG. 2 is a view on line 22 of FIG. 1, partly in fragmentary section and partly in elevation;

FIG. 3 is an exploded perspective view showing the parts of the abrasive unit of the present invention; and

FIG. 4 is a side view of the abrasive unit of FIG. 3 showing its arcuate shape.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2, the rotary abrasive tool or wheel of the present invention includes a central hub 11 which has a central bore 12 for receiving a shaft 13. The shaft 13 is adapted to be attached to a source of power for rotating the tool inside a cylinder 14 or the like. The hub 11 is preferably made of nylon or other suitable plastic and has a peripheral surface 15 with a plurality of equally spaced longitudinal slots 16 formed therein for receiving a plurality of preassembled abrasive units 20. The slots 16 are formed for retaining the units 20 against movement in the radial direction, and for this purpose may have narrow necks 21 opening into circular undercuts 22 (FIG. 2).

Each abrasive unit 20 includes a pad 23 of overlying abrasive-coated cloth or paper plies 25 which are held tightly together by a clip 26 at their inner ends. The anchor clip 26 is formed for slidable endwise insertion into the slots 16, and preferably comprises a piece of metal having a circular portion 27 terminating in outwardly extending and generally parallel flanges 28. The plies 25 are riveted between the flanges 28 with a fastening member 29, and their inner ends, which are substantially aligned, are positioned in generally abutting relation to the circular portion 27.

After each of the slots 16 is supplied with an abrasive unit 20, a pair of side disks 30 are secured to the sides of the hub 11 and retain the abrasive units 20 in the slots and restrain them against axial movement during rotation of the too]. As shown in FIGS. 1 and 2, a pair of bolts 31 may be threaded on the shaft 13 and tightened against the disks 30 to hold them against the sides of the hub 1 1.

In accordance with the present invention, the plies 25 in each pad 23 are all assembled facing in the same direction, and each overlying ply 25 is of successively shorter length. The plies 25 therefore form at their outer ends multiple stepped or staggered abrading surfaces 35 which combine to define an overall self-dressing abrading surface 40 for contact with the internal surface of the cylinder 14.

In the preferred embodiment of the invention, the plies 25 are bowed into an arcuate shape and a predetermined flexibility by breaking them over a roller or rollers at various angles with respect to their longitudinal axes. The arcuate shape enlarges the exposed area of the individual abrading surfaces 35 and permanently sets the plies with a curvature adapted for tangential engagement with the work surface. In addition, the

area of the overall abrasive surface 40 is increased on each abrasive unit, and this gives the abrasive units an expanded service life capability.

The plies 25 are preferably cut from a web of abrasivecoated cloth which has been broken over three separate rollers to a high degree of flexibility. To soften its inherent rigidity, the web is first broken over a roller at an angle of 90 with respect to its direction of travel. It is then passed over second and third rollers at angles with respect to its direction of travel of 45 to one side and 45 to the other side, respectively.

The three roller passes give the plies 25 a triple degree of flexibility which enables them to flex when they are deflected by burrs or imperfections protruding from the work surface, thereby substantially eliminating the scratching problem caused by rigid abrasive plies. Moreover, this increased flexibility, when coupled with the increased exposed abrading area created by the curvature in the plies, also serves to wipe the work surface more effectively and to produce high quality abrasive finishes.

From the drawing and the above description, it is apparent that certain advantages and features are provided by the present invention. Because the pad as a whole is arcuate and the plies have different lengths, the outer ends of the plies are essentially preadjusted so all the abrading surfaces in each pad will tangentially contact the work surface as it is rotated inside a cylinder. Moreover, centrifugal force rather than the inherent bias in the plies will urge the plies radially outwardly to engage the work surface, and this feature is particularly advantageous when the tool is shifted to a different diameter cylinder.

The curvature of the plies increases the contact area of the multiple exposed surfaces in each pad and provides improved wiping and polishing characteristics, and it also expands the service life of the pads. Because the curvature provides flexibility at points relatively close to the peripheral surface of the hub, the pads may be worn down very close to the hub. For example, a polishing unit in which the bottom ply is 4.0 inches long may be used until this ply is worn down to a length of about 1.0 inch.

In addition, the self-dressing service life is increased because the abrasive material contacts the work surface tangentially, rather than obliquely, and the abrasive material wears down smoothly instead of being sheared off at the outer edges. The abrasive material is not worn off as quickly and therefore lasts longer.

The softened plies are well suited for finishing and polishing operations, but at the same time they can deburr by cutting into protrusions on the surface, and their flexibility will prevent them from scratching the adjacent work surface. Accordingly, the increased flexibility in the abrasive tool of the present invention improves its performance in each of the deburring, finishing and polishing functions.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A rotary abrasive tool comprising:

a. a central hub,

b. a plurality of arcuately curved abrasive units attached to and extending outwardly in curved paths from said central hub,

c. each of said abrasive units comprising:

i. a plurality of plies of abrasive covered backing materials,

ii. means engaging inner ends of said plies and maintaining said plies in laminar relationship to each other with said inner ends substantially aligned, and

iii. said plies being of progressively increasing lengths from the outermost ply in each curved unit to the innermost ply thereof and defining a stepped, outer curved surface.

2. The ro ta abrasive tool of claim 1 wherein: a. said plies ave a predetermined flexibility. 

1. A rotary abrasive tool comprising: a. a central hub, b. a plurality of arcuately curved abrasive units attached to and extending outwardly in curved paths from said central hub, c. each of said abrasive units comprising: i. a plurality of plies of abrasive covered backing materials, ii. means engaging inner ends of said plies and maintaining said plies in laminar relationship to each other with said inner ends substantially aligned, and iii. said plies being of progressively increasing lengths from the outermost ply in each curved unit to the innermost ply thereof and defining a stepped, outer curved surface.
 2. The rotary abrasive tool of claim 1 wherein: a. said plies have a predetermined flexibility.
 3. The rotary abrasive tool of claim 1 wherein said abrasive units are attached to said hub by means of: a. an integral anchor clip having a central portion and parallel flanges extending therefrom, b. a fastening member securing said inner ends of said plies between said flanges, and c. a plurality of peripherally spaced slots in said central hub receiving said clips.
 4. The rotary abrasive tool of claim 3 further comprising: a. retaining disks mounted on opposite faces of said central hub and retaining said clips in said slots. 